| 摘要 |
PURPOSE:To stabilize the accuracy of the positioning of head against thermal/ humidity variation by forming the virtual line from the point of fixation of the carriage and the driving belt to the recording/reproducing point of the magnetic head and the virtual line from the center of the driving pulley to the center of the disc parallel and by forming the driving pulley with invar. CONSTITUTION:The distance from the center point H of the magnetic disc 15 to the position of track E of the disc, and that from the center of driving I of the driving pulley 18 to the fixation point F where the carriage 13 and the driving belt 16 are fixed together, are made an equal length J. And distance from the disc center H to the center I of the driving pulley 18 is made of a length K. In effect by the above formation, the aberration of the length K due to thermal extension/shrinkage little causes an off tracking. Also, invar of which thermal expansion is extremely small is used as the material of the driving pulley 18, and further the linear expansion coefficient of the magnetic disc 15 and that of the driving belt 16 are made to approximately coincide. Therefore, the off tracking of the magnetic head against the magnetic disc caused by the environmental temperature variation is approximately annihilated.
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